One suggestion, would be to, in some fashion. Show the user that there are multiple levels of acceptable passwords. without knowing that there are 5 levels, a use may simply stop at the first green level, and not know they could make something stronger.

this is a cool thing as passwordstrength is an important one to prevent being hacked.

While testing it i have an issue from usability:

* if you color the background it's difficult to see the input, it would be needed to calculate the complementary color for text color
* the colors are fancy but need description. The user might think: That's funny, i get changing colors. But he don't understand what's about, you would need to descibe that.

I think the simplest way to display passwordstrength is kind of filled bar beside withbad .......... good label beside, so it's easy to understand while typing.

I modified the code from 1.x forum ( here: http://www.sencha.com/forum/showthre....PasswordMeter ) . I created a password meter widget that is Ext 4 compatible. You can check it from my blog post.
With a quick test, it works fine. I have not done extensive test on it. Please let me know if you test on it and find any issue.